Various designs of quick acting closures (clamp type, clutch type, screw type and bridge type) have been utilized on pressure vessels, including pipelines, within the chemical, oil and gas, food, and nuclear industries. The demand to frequently obtain access to pressure vessels has been increasing, thereby enhancing the need for a safe closure that provides quick opening and closing/sealing capabilities.
Examples of prior art closures are disclosed in U.S. Pat. Nos. 5,127,535; 4,387,740; 4,693,278; 4,815,627; 4,883,637; 4,315,577. Many of these prior art designs are similar in concept, but are complex, difficult to manufacture and operate, and/or require removal of material from critical pressure retaining surfaces that prevent compliance with international design codes. In addition, these prior art designs do not and some practically cannot incorporate an integral safety locking feature that prevents unsafe handling and operation of the closure. European Patent Specification 0129349 discloses a closure which does include a safety locking feature, although the closure does not overcome many of the other deficiencies with prior art closures.
The disadvantages of the prior art are overcome by the present invention, and an improved closure and method of closing a door on a pressure vessel are hereinafter disclosed.